Dean Kamen on Clean Energy, Clean Water, and Commuting in the Mega City (Part Two)

With his planes, helicopters, and other fuel-hungry pets, Dean Kamen admits that he takes a lot out of the world. This just means that, in keeping with his immigrant grandfather's advice, he has to put more back in. In the second part of our conversation, Kamen shares his obsession with the Sterling engine, telling about the one rigged into his electric car, the ones stationed in Bangladeshi villages, and the 80,000-pound Sterling sitting in his living room. The maverick inventor also lets us in on his vision of the future, which will see many of our problems evaporate, and new ones born.

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Full text after the jump.TreeHugger: If you recall in Back to the Future II, Doc has the DeLorean rigged up with the Mr. Fusion, and he's throwing banana peels and Miller High Life in there. This seems a lot like how you describe the Sterling Engine. What is a Sterling engine?

Kamen: Very basically, as a physicist, I would tell you that a Sterling engine is a heat engine which extracts energy from heat and turns it into mechanical work like other heat engines—like the Braden cycle or the Rankine cycle or the Otto cycle or the Diesel cycle. But, it does it as an external combustion device. The fuel that heats the gas inside the engine never goes inside the engine itself.

As a consequence, the Sterling thermodynamic cycle allows you to use a much broader range of fuels because they don't have to be compatible with the inside workings of your engine. They don't have to be mixed with air in such a ratio as to get the kind of spark ignition or compression ignition that you have in the kinds of engines in cars and trucks.

It allowed us to build an engine that could use many, many more different kinds of fuels, particularly ones that would be locally available around the world: anything from olive oil to cow dung to methane gas. And even when it did burn available fuels—like diesel, kerosene, or gasoline—it burns them in a continuous combustion, like your kitchen stove as opposed to the explosions, the bang, bang, bang of your diesel, we can burn them much more cleanly with much less environmental impact than when they are burned in other thermodynamic cycles.

TreeHugger: I've seen you present the Sterling engine as a solution for stationary power generation that can be fed with a vast array of available fuels. "Anything that burns" is how you said it.

Kamen: In fact we had two villages in Bangladesh that we ran for 24 weeks in an experiment with our Sterling engine. As you say, it was stationary power in these little villages. And the only fuel that those engines burned during that time was the methane gas evolving off piles of cow dung that were put into pits next to the engine. Had those pits just allowed that methane to evolve as it would anyway, methane gas is 21 times as bad for the environment as carbon dioxide as a greenhouse gas. And then it turns into carbon dioxide anyway.

So we collected that methane, burned it locally to heat up one end of our engine, literally like you burn methane in your camper stove. And we made electricity and eliminated the methane gas.